A vacuum interrupter, which is a core component of a vacuum breaker, comprises, as shown by FIG. 1, a generally barrel-shaped insulating housing 51 made of inorganic insulative materials like ceramic or glass. The insulating housing 51 is sealed on both ends thereof with metallic cover plates 52 and forms a closed container. The interior of the closed container is provided with a static contact 54 fixed on a static conductive rod 53 and a moving contact 56 fixed on a moving conductive rod 55. A corrugated pipe 57 is sealed between the moving conductive rod 55 and the metallic cover plate 52. The moving conductive rod 55 moves along its axial direction to drive the moving contact 56 to cooperate with the static contact 54 and finish opening and closing actions. A shielding cap 58 is provided surrounding the contacts and the corrugated pipe 57, in order to provide a uniform internal electric field distribution and reduce the evapotranspiration contamination of metal vapor.
During the opening of the contacts, vacuum arc is generated between the contacts. The vacuum arc is maintained by metal plasma evaporated from the contacts. When the power frequency current crosses zero, the metal vapor will stop evaporating, meanwhile the vacuum arc is extinguished since the plasma of the arc diffuses rapidly to the surroundings, and the clearance between the contacts becomes an insulator quickly; thus the current is interrupted and the metal vapor generated during arcing is condensed by the surface of the shielding cap 58. However, it is difficult for the existing vacuum interrupter to maintain a better voltage withstanding in high voltage and ultra-high voltage environment due to the limitations of its construction, so that it is hindered in the development towards high voltage and ultra-high voltage.